The document discusses plutonic rocks. Plutonic rocks are igneous rocks that solidified from a melt at great depth within the Earth's crust. They cool slowly, allowing crystals to grow large. Plutonic rocks include granite, gabbro, diorite, and pegmatite. Granite is a common plutonic rock composed of quartz, feldspar, and mica. Pegmatite is a very coarse-grained rock that can contain large masses of feldspar, quartz, and mica. Plutonic rocks are the most common rocks on Earth and form the basis of continents and mountain ranges.

1. Plutonic Rocks
Group 2 Presentation

2.  Group 2 Members
 1- Nuur xabiib cumar 226
 2- Muumin Abdulle Abdi 275
 3- Khalid Hirabe Mumin 236
 4- Ruweydo Ali Yusuf 274
 5- Abduqafar Aadan xareed 348
 6- Mohamed Yusuf gedi 304
 7- Hassan Daheir Mohamud 330

3. Plutonic rocks
Plutonic rocks are igneous rocks that solidified from a melt at
great depth. Magma rises, bringing minerals and precious
metals such as gold, silver, molybdenum, and lead with it,
forcing its way into older rocks. It cools slowly (tens of
thousands of years or longer), underneath Earth's crust, which
allows the individual crystals to grow large by coalescing, like
with like; thus, plutonic rock is coarse-grained rock. The rock
is later exposed by erosion. A large body of this type of rock is
called a pluton.

4. What Does "Plutonic"
Mean?
The name "plutonic" refers to Pluto, Roman god of wealth and
the underworld; pluto's origins also come from "wealth," or
"rich one," which could refer to the precious metals present in
the Earth and in rocks. Gold and silver are found in veins in
plutonic rocks, which are formed from the intrusions of the
magma.
In contrast, volcanic rocks are formed by magma above
ground. Their crystals are evident only through an
examination under a microscope.
The dwarf planet Pluto, however, is mostly ice made up of
frozen nitrogen, methane, and carbon dioxide, though it may
have a rocky core that contains some metals.

5. How to Identify
The main way to tell a plutonic rock is that it's made of tightly
packed mineral grains of medium size (1 to 5 mm) or larger,
which means that it has phaneritic texture. In addition, the
grains are of roughly equal size, meaning that it has an
equigranular or granular texture. Finally, the rock is
holocrystalline—every bit of mineral matter is in a crystalline
form, and there is no glassy fraction. In a word, typical
plutonic rocks look like granite. In fact, producers of building
stone classify all plutonic rocks as commercial granite.

6. The Most Common Rocks on Earth
Plutonic rocks are the most common rocks on Earth and form the
basis of our continents and roots of our mountain ranges.
The large mineral grains in plutonic rocks don't generally have
well-formed crystals because they grew crowded together—that
is, they are anhedral. An igneous rock from a shallower depth
(with grains smaller than 1 mm, but not microscopic) may be
classified as intrusive (or hypabyssal), if there's evidence that it
never erupted onto the surface, or extrusive if it did erupt. As an
example, a rock with the same composition could be
called gabbro if it were plutonic, diabase if it were intrusive, or
basalt if it were extrusive. Whereas plutonic rocks form
continents, basalt lies in the crust underneath the oceans.

7. There Are About a Dozen Major
Types
The name for a particular plutonic rock depends on the mix of
minerals in it. There are about a dozen major plutonic rock
types and many more less common ones. In ascending order,
four types include gabbro (dark in color, not much silica),
diorite (an intermediate amount of silica), granite (68 percent
silica), and pegmatite. Types are classified according to various
triangular diagrams, starting with one based on the content of
quartz (which is pure silica) and the two types of feldspar
(which is quartz with impurities).

8. Examples of Plutonic
Rocks
Granite is a coarse or medium- grained rock, composed of quartz, an acid
feldspar or two of them (orthoclase, microcline, albite), and generally
mica (biotite, or muscovite, or both). Instead of the whole or a part of
the mica, there may be hornblende, or, rarely, pyroxene (augite). The
commonest granite is that composed of quartz, feldspar, and black mica
(biotite), and white mica (muscovite). Other varieties are biotite-granite,
with black mica only; muscovite-granite, with white mica only;
hornblende granite etc. These rocks contain 65% to 80% silica.
• Granite

9. Examples of Plutonic
Rocks
• Pegmatite
is a name given to very coarse-grained rocks, commonly of
the composition of granite; but there are also syenite-
pegmatites and diorite-pegmatites. Pegmatite often contains
large masses of pure feldspar, quartz, and mica, which can
be quarried out separately. Pegmatite may carry tinstone,
wolframite, scheelite, zircon, topaz, uranium-radium ores,
etc.